In recent years, for example, the markets expansion of imaging devices having solid-state image sensing device such as a digital still camera and a digital video camera, is remarkable. The number of the pixels of the solid-state image sensing devices (for example, the image sensing devices such as a CCD and a CMOS) used in such imaging devices, noticeably increases.
On the other hand, the technique for recording moving image at a high frame rate from the solid-state image sensing device having the very large number of the pixels (herein after also referred to simply as “high-pixel image sensing device”) does not much make progress.
Therefore, in the imaging device such as a digital still camera having the high-pixel image sensing device, although the image sensing device has the very large number of the pixels, there is the problem that there is a limit in the number of the pixels (the number of the signals) which are readout as moving image.
For this reason, in the imaging device such as a digital still camera, in order to reduce the number of the pixels (the number of the signals) that are readout from the high-pixel image sensing device, a down sampling readout method and a pixel mixture method are conventionally utilized.
The down sampling readout method is a method for down sampling and reading out the pixels of the image sensing device having a CFA, simply. Further, the pixel mixture method is a method for mixing multiple pixels in an image sensing device having a CFA and reading out the mixed pixel as one pixel value (signal). At this time, for example, in pixel mixture methods disclosed in Non-Patent Document 1 and Patent Document 1 (herein after also referred to simply as “conventional methods”), the pixels having the same color in the image sensing device are mixed. Here, such conventional methods are called as “same-color-pixel mixture” or “same-color-pixel mixture method”.
There are the following problems in the conventional same-color-pixel mixture methods.
For example, in the case where the conventional same-color-pixel mixture method is applied to the solid-state image sensing device having a color filter array (CFA) with Bayer pattern, since it is necessary to mix several pixels that are spatially separated, a problem that the resolution is degraded and the high-definition image cannot be obtained, occurs.
In order to solve the above problem, for example, in an imaging device disclosed in Patent document 2, a pixel mixture method for mixing four pixels that are adjacent spatially, is disclosed. However, in the case of using this pixel mixture method disclosed in Patent Document 2, there is a problem that the kind of CFA which can obtain an effective output, i.e. the high-definition image, is limited.
For example, it is impossible to apply the pixel mixture method disclosed in Patent Document 2 for Bayer pattern which is used as a color filter array (CFA) widely now. This is because in the case of applying the pixel mixture method disclosed in Patent Document 2 to the solid-state image sensing device having a CFA with Bayer pattern, the kind of the colors after mixture becomes one kind.